The present invention relates to a cutting insert for longitudinal turning, inwards copy-turning, turning of grind reliefs and outwards copy-turning or for a combination of two or more of said machining operations. The cutting insert mainly has rhombic or triangular basic shape comprising at least on cutting corner, at least one nose portion arranged in the cutting corner and two main cutting edges connected to the nose portion. The main cutting edge has a mainly straight contour in the area which is closest to the connection to the nose portion and the nose portion is expanded in the width direction at an acute-angled cutting corner symmetrically around the bisector thereof, such that the setting angle and/or the clearance angle will be locally large during machining of a work piece.
Conventional cutting inserts for use in the above-mentioned turning operations present drawbacks during machining of a work piece. Poor surfaces are generated at inwards copy-turning and longitudinal turning due to friction between the surface of the work piece and the side of the cutting insert because the clearance angle thereof is too small. The chip control becomes poor at outwards copy-turning as the chips will get broad and thin with a cutting insert having a small setting angle relative to the work piece surface. Furthermore the straight sides of the cutting insert render keyway slotting practically impossible.
The object of the present invention is to provide a cutting insert for turning, which solves the above-mentioned problems.